Abrading – Precision device or process - or with condition responsive... – With indicating
Reexamination Certificate
1999-10-26
2001-12-04
Eley, Timothy V. (Department: 3723)
Abrading
Precision device or process - or with condition responsive...
With indicating
C451S010000, C451S011000, C451S005000
Reexamination Certificate
active
06325699
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a lapping method and a lapping apparatus for compensating a warp of a work during a lapping process of the work, and more particularly to a lapping method and a lapping apparatus for consecutively compensating the warp of the work while automatically lapping the work.
2. Related Background Art
A magnetic thin film head has hitherto been lapped after forming the magnetic thin film head in, e.g., a process of manufacturing the magnetic head. In this lapping process, heights of a gap and of a magnetic resistance layer of the magnetic thin film head are uniformly lapped.
An accuracy as hyperfine as sub-micron is required of the heights of the gap and of the magnetic resistance layer. The lapping apparatus is therefore required to automatically lap the work at a high accuracy.
FIGS.
17
A~
17
B and
18
A~
18
D are explanatory views showing a process of manufacturing a composite type magnetic head.
As illustrated in
FIG. 17A
, rows
101
of a multiplicity of composite type magnetic heads are formed on a wafer
100
by a thin film technology. The composite type magnetic head
101
is composed of a magnetic resistance element and an inductive writing element which are provided on a substrate.
Next, as shown in
FIG. 17B
, the wafer
100
is cut in strips, thereby forming a row-bar
101
. This row-bar
101
is constructed of one row of magnetic heads
102
. Further, resistance elements (ELG elements)
102
a
for a lapping monitor are provided at a left end, a center and a right end of the row-bar
101
.
In the magnetic head
102
, it is required that a resistance value of a magnetic resistance film of each magnetic head be adjusted to a fixed value. Therefore, a height of the magnetic resistance film is lapped to a fixed value. The row-bar
101
is, however, extremely thin, and a thickness thereof is on the order of, e.g., 0.3 millimeter. Accordingly, it is difficult to directly fit the row-bar to a lap jig. Hence, as shown in
FIG. 17C
, the row-bar
101
is bonded to a transfer tool
103
by use of a thermal fusion wax.
Then, as shown in
FIG. 18A
, the row-bar
101
is placed on a lap plate
104
and lapped. At this time, as known from Japanese Patent Application Laid-Open Publication No.2-124262 (U.S. Pat. No. 5,023,991) and Japanese Patent Application Laid-Open Publication No.10-286765, a resistance value of the ELG element
102
a
of the row-bar
101
is measured throughout the lapping process. Then, the measured resistance value is converted into a height of the magnetic resistance film of the magnetic head
102
, and it is detected whether or not the height reaches a target height.
When it is detected through the measurement of the resistance value that the magnetic resistance film is lapped to the target height, the lapping process is terminated. Thereafter, as shown in
FIG. 18B
, a slider is formed on a lower surface
101
-
1
of the row-bar
101
.
Further, as shown in
FIG. 18C
, with the transfer tool
103
remaining fitted, the row-bar
101
is cut into each magnetic head
102
. Then, as illustrated in
FIG. 18D
, each magnetic head
102
is taken out while fusing the thermal fusion wax by heating the transfer tool
103
.
The row-bar
101
constructed of one row of magnetic heads
102
is formed, and thereafter the lapping process is executed on the unit of the row-bar
101
, whereby the magnetic resistance films of the multiplicity of magnetic heads
102
can be lapped at one time.
FIGS. 19A and 19B
are explanatory views showing the prior art.
As shown in
FIG. 19A
, the row-bar
101
is 0.34 mm thick and 1.2 mm wide. As compared with these dimensions, its length is as long as 40.7 mm, and therefore a warp (bend) is easy to occur in a longitudinal direction. So, it is difficult to ensure straightness which is as precise as sub-microns. Namely, there might be an error in a bonding accuracy in a bonding process of bonding the row-bar
101
to the dedicated transfer tool
103
. Further, there is also a limit in terms of a bonding surface accuracy of the transfer tool
103
. This might become hindrance against uniformization of lapping accuracy especially of the magnetic resistance element.
Such being the case, the following warp compensating method is proposed in the specification of Japanese Patent Application Laid-Open Publication No.10-286765. As shown in
FIG. 19B
, the warp compensating involves applying a bend pressure to the central position of the transfer tool
103
, and making the transfer tool
103
deformed. Therefore, a bending mechanism for applying the bend pressure is provided in the central position of the transfer tool
103
.
Then, a warp quantity of the row-bar
101
attached to the transfer tool
103
is detected by an optical method etc. before the lapping process. Subsequently, the bending mechanism bends the transfer tool
103
so that the detected warp quantity comes to zero during the lapping process. This bending mechanism involves the use of a mechanism for converting a quantity of rotation into displacement by utilizing a screw.
There arise, however, the following problems inherent in the prior art.
First, the transfer tool
103
is formed with a hole for fitting to the lap jig. Therefore, when a lapping pressure is applied to the transfer tool, a warp occurs due to the tool hole. That is, when the lapping pressure is applied, a large pressure is generated at both side ends of the row-bar
101
, resulting in a difficulty of lapping the central portion of the row-bar
101
. If the lapping continues as it is, the lapping pressure of the row-bar becomes constant, and the work is lapped with the warp remaining occurred. The prior art has such a problem that the warp occurred during the lapping process can not be compensated because of using the warp quantity measured beforehand. Further, there is needed a labor for measuring the warp quantity beforehand.
Second, the bending mechanism involves the screw mechanism in the prior art. Therefore, a problem is that it is difficult to compensate a minute quantity of warp. Moreover, when giving a force for rotating the screw, the lap jig for holding the transfer tool rotates. Because of being incapable of controlling this, the lapping accuracy declines. Further, an excessive pressure is applied to the lap jig, and consequently a smooth lapping process is hard to attain.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a lapping method and a lapping apparatus capable of compensating a warp of a work occurred during a lapping process.
It is another object of the present invention to provide a lapping method and a lapping apparatus capable of compensating a minute quantity of warp of a work.
It is a further object of the present invention to provide a lapping method and a lapping apparatus capable of preventing an excessive pressure from being applied to a lap jig even when applying a pressure for compensating the warp.
To accomplish the above objects, according to a first aspect of the present invention, a lapping method comprises a step of detecting a warp quantity of the work during a lapping process, and a step of controlling a force of pressurization to be applied to the work so that the detected warp quantity becomes a target value.
According to the present invention, first, the warp quantity of the work is compensated by detecting the warp quantity of the work during a lapping process. It is therefore feasible to compensate the warp occurred during the lapping process. Further,before the lapping process, a labor for measuring the warp quantity of the work can be saved.
According to a second aspect of the present invention, the controlling step comprises a step of controlling a fluid pressure of bending means for applying a pressure to the work.
The bending means involves the use of a mechanism for applying the pressure to the work in accordance with a fluid pressure. The minute quantity of warp can be thereby compensated, and the warp quantity can be controlled down to zer
Sudo Koji
Sugiyama Tomokazu
Yanagida Yoshiaki
Eley Timothy V.
Fujitsu Limited
Greer Burns & Crain Ltd.
Nguyen Dung Van
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